A line of storms have already been experienced from the Blue Mountains to the south coast, with rainfall of up to 40 millimetres in half an hour recorded, as well as wind gusts of up to 100km/h.

Weatherzone senior meteorologist Jacob Cronje also said Tuesday's thunderstorms were not expected to be as severe, but "any thunderstorm can produce hail".

"Specific severe weather is not necessarily expected from these [storms], but having said that, thunderstorms could produce strong winds and heavy rain, localised heavy falls and hail," he said.

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Temperatures in Sydney were forecast to reach 29 degrees on Tuesday and 28 on Wednesday, while tops of 33 degrees are expected on both days in the west.

While warm, the temperatures and storms are a far cry from the 40 degrees reached in the city on Saturday, and the damaging hailstorm that hit the coast of NSW just before Christmas.

A reprieve from thunderstorms and rain is expected on Saturday, with a forecast for a mostly sunny day and tops of 29 degrees in the city, but 35 degrees and the slight chance of a shower in the west.

The thunderstorms forecast for Tuesday came on the back of fog that covered some parts of Sydney in the morning.

"It wasn't necessarily thick, but there were wisps of it around," Mr Cronje said.

The senior meteorologist said the morning fog was expected given the rainy and warm conditions.

"Whenever we’ve had rain and it's hot enough, and there's no cloud overnight and it's clearing in the morning, that's a notorious fog formation," he said.

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